Descreening using segmentation-based adaptive filtering

3 February 2011 Descreening using segmentation-based adaptive filtering

Mohamed N. Ahmed, Ahmed H. Eid

Author Affiliations +

Proceedings Volume 7870, Image Processing: Algorithms and Systems IX; 78700E (2011) https://doi.org/10.1117/12.872516
Event: IS&T/SPIE Electronic Imaging, 2011, San Francisco Airport, California, United States

Abstract

Ordered halftone patterns in the original document interact with the periodic sampling of the scanner, producing objectionable moir´e patterns. These are exacerbated when the copy is reprinted with an ordered halftone pattern. A simple, small low-pass filter can be used to descreen the image and to correct the majority of moir´e artifacts. Unfortunately, low-pass filtering affects detail as well, blurring it even further. Adaptive nonlinear filtering based on image features such as the magnitude and the direction of image gradient can also be used. However, non careful tuning of such filters could either cause damage to small details while descreeing the halftone areas, or result in less descreening while sharpening small details. In this paper, we present a new segmentation-based descreening technique. Scanned images are segmented into text, images and halftone classes using a multiresolution classification of edge features. The segmentation results guide a nonlinear, adaptive filter to favor sharpening or blurring of image pixels belonging to different classes. Our experimental results show the ability of the non-linear, segmentation driven filter of successfully descreening halftone areas while sharpening small size text contents.

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Mohamed N. Ahmed and Ahmed H. Eid "Descreening using segmentation-based adaptive filtering", Proc. SPIE 7870, Image Processing: Algorithms and Systems IX, 78700E (3 February 2011); https://doi.org/10.1117/12.872516

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